Silo type storage tanks are commonly used for containing foodstuffs during processing and/or storage. These tanks can be quite large, ranging from a little over eight feet to a little over twelve feet in diameter in a typical application, and up to a little over twelve feet tall. In order to meet sanitary standards set by a number of regulatory agencies, including 3-A and the USDA, it is necessary that all of their internal surfaces be amenable to being completely cleaned on a periodic basis. One prior art device that has been provided to accomplish this includes a spray nozzle and spray dish located at the top center of the tank, wherein the cleaning fluid sprays through the nozzle and is deflected off the spray dish and against the top and sidewalls to cascade the cleaning fluid down the tank surfaces to thereby clean them. A supply line carries the cleaning solution from the alcove, up the outside of the tank, through the top head, and onto the spray dish. This arrangement requires a ladder, cage, guardrail, and possibly a catwalk to gain access for maintenance and inspection, thus entailing an added layer of expense and inconvenience. In some applications this cleaning apparatus is removable, which then further increases the expense due to the need for ferrules, clamps, and gaskets to accommodate its disassembly/re-assembly. Another attempt in the prior art to address this cleaning problem is shown in U.S. Pat. No. 4,192,332 which discloses a jet spray nozzle located in the lower portion of the tank, extending inwardly from the alcove area. With this device, cleaning fluid is sprayed through spray nozzles at high pressure upwardly against the top and upper sidewalls of the tank so that it may cascade down and clean. This device is similar to a spray ball and requires high pressure and flow rates, all of which again increases the initial cost and on-going operating expense.
These various prior art attempts to solve the cleaning problem all suffer drawbacks which heretofore were unavoidable. They require in some cases significant structural devices (ladders, etc.) which are unsightly, costly, and entail some degree of risk for the workman who must inspect and maintain the cleaning system. Alternately, with the spray ball device, a rather complicated device must be provided which again represents a significant expense, and which itself must be removable from the tank for it to be cleaned and to avoid interference with the operation of the tank. Furthermore, there must be periodic inspection and maintenance. Neither of these approaches allow for the cleaning operation to be conducted automatically and without an operator getting physically involved at some point in time either for operation or maintenance.
In order to solve these and other problems in the prior art, the inventor has succeeded in designing and developing a clean-in-place fixture for a silo type storage tank which is elegantly simple, which eliminates the need for operator intervention, which is self cleaning, which has no special structure requiring expensive manufacture or maintenance, and which effectively cleans all interior surfaces of the tank while remaining fixed in place and without interfering with the operation of the tank. Essentially, the present invention comprises a channel, duct, tube, or other passageway which is located near the top of the tank and which has an xe2x80x9cangle of attackxe2x80x9d such that a spray emanating therefrom effectively sprays the tank top and virtually the entirety of the tank sidewalls. An overflow tube, which is preferably a vertically oriented standpipe, has its mouth located adjacent the channel outlet so that cleaning fluid overflows out of the tube and against the sidewall just beneath the channel outlet to wash the sidewall beneath it, as well as the outer surfaces of the overflow tube itself The overflow tube thus cleans that small portion of the tank interior which may be missed by cleaning fluid spraying out of the channel.
The xe2x80x9cangle of attackxe2x80x9d and physical location for the channel may be readily determined in the field for any particular tank size and dimension. However, the inventor has determined that a particular location and xe2x80x9cangle of attackxe2x80x9d works well with a broad range of tank sizes, and thus represents his preferred embodiment as explained below. By xe2x80x9cangle of attackxe2x80x9d is meant that angular orientation of the channel with respect to the interior tank sidewall. The inventor has also determined a channel size as his preferred embodiment which will provide an effective cleaning using the expected flow rates and pressures that have been adopted in the industry. Thus the present invention is readily adaptable to any existing or new installation without the need for extensive considerations of cleaning fluid pumps or supplies. It has also been determined that these factors are somewhat interrelated such that changing one may be accommodated for by changing another, and yet provide an effective cleaning. Therefore, there is some flexibility in the implementation of the present invention which will allow for user or designer preference.
Thus, the present invention represents a significant advance over the prior art by eliminating structural devices, thereby providing an elegantly simpler device at less cost, maintenance, and with greater flexibility in implementation. While the principal advantages and features of the invention have been briefly explained above, a greater understanding of the invention may be attained by referring to the drawings and description of the preferred embodiment which follow.